1. Field of the Invention
The present invention relates to a liquid discharge head for use in a printer or video printer which is used as an output terminal for a copying machine, facsimile apparatus, word processor or host computer, a manufacturing method for said liquid discharge head, a head cartridge having said liquid discharge head mounted thereon, and a liquid discharge apparatus. In particular, this invention relates to a liquid discharge head comprising a substrate formed with electrothermal converting elements for producing heat energy for use as the energy for recording, which performs the recording by discharging the recording liquid (ink or the like) as flying liquid droplets from the discharge openings (orifices) onto the recording medium, a manufacturing method for said liquid discharge head, a head cartridge having said liquid discharge head mounted thereon, and a liquid discharge apparatus.
Note that xe2x80x9crecordingxe2x80x9d in this invention means applying meaningful images such as characters or figures, as well as other images such as patterns, onto the recording medium.
2. Related Background Art
An ink jet recording method or so-called bubble jet recording method has been conventionally well-known, which forms the image by applying the heat energy to cause the state change accompanying rapid volume change to occur in the ink and discharging the ink from the discharge openings using working force by this state change of ink. A recording apparatus relying on this bubble jet recording method is typically provided with discharge openings for discharging the ink, and ink flow channels in communication with these discharge openings, and heating elements (electrothermal converting elements) as energy generating means for discharging the ink disposed in the ink flow channels, as disclosed in U.S. Pat. No. 4,723,129.
With such recording method, a high quality image can be recorded at high speed and with low noise, and because the head for this recording method allows the discharge openings for discharging the ink to be arranged at high density, there are many good advantages such as easily producing a recording image of high resolution, or, further, a color image, with a small apparatus. Therefore, this bubble jet recording method has been recently utilized for many types of office equipment such as printers, copying machines, and facsimile apparatus, and further has come into use for industrial systems such as printing machines.
Development of this bubble jet technology into a variety of products has raised the following various demands in recent years.
For example, examining the request to improve the energy efficiency includes regulating the thickness of the protective film in the heating element. This examination is effective in improving the efficiency of transferring the produced heat to liquid.
In order to obtain a high quality image, there have been proposed the driving conditions to provide a liquid discharge method which is capable of discharging the ink excellently based on the stable production of bubbles, with high rate of discharging the ink, and from the viewpoint of high speed recording, the improved shape of liquid flow channels to obtain a liquid discharge head with high rate of filling the ink to be discharged into the liquid flow channels.
Turning back to the principle of discharging the liquid, careful research has been made to provide a novel liquid discharge method using the bubbles that have never been obtained conventionally, and a head for use therewith, as proposed in Japanese Patent Application Laid-Open No. 9-201966.
In the following, a conventional liquid discharge method and a head for use therewith as disclosed in Japanese Patent Application Laid-Open No. 9-201966 will be described with reference to FIGS. 19A to 19D. FIGS. 19A to 19D are views for explaining the discharge principle in a conventional liquid discharge head, or a cross-sectional view taken in a direction of liquid flow channels. Also, FIG. 20A is a perspective view, partially broken, of the liquid discharge head as shown in FIGS. 19A to 19D. The liquid discharge head as shown in FIGS. 19A to 19D is the most fundamental constitution for enhancing the discharge power or discharge efficiency by controlling the propagation direction of pressure caused by bubble or the growth direction of bubble in discharging the liquid.
Note that xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d as used in the following description are taken with respect to the flow direction in which liquid passes from a liquid supply source via above a bubble producing region (or movable member) to the discharge openings.
The term xe2x80x9cdownstreamxe2x80x9d in respect of a bubble itself is represented by the portion of bubble on the discharge opening side which is supposed to directly take effect in the discharging of a liquid droplet. More specifically, it means the bubble produced in the heating element downstream in the flow direction as above or the constitutional direction relative to the center of bubble, or in the downstream region from its areal center.
Furthermore, xe2x80x9ccomb toothxe2x80x9d refers to the shape having the support of a movable member as a common member and its free end opened.
In an example of FIGS. 19A to 19D, a liquid discharge head is provided with a heat generator 1102 for applying heat energy on the liquid, as the discharge energy generating element to discharge the liquid, on an element substrate 1101, a liquid flow channel 1103 being disposed, corresponding to the heat generator 1102, above this element substrate 1101. The liquid flow channel 1103 is in communication with a discharge opening 1104, as well as a common liquid chamber 1105 for supplying the liquid to a plurality of liquid flow channels, from which the liquid in an amount corresponding to the liquid discharged from the discharge opening 1104 is received.
On the element substrate 1101 in this liquid flow channel, a planar movable plate 1106 made of elastic material such as metal is provided opposed to the heat generator 1102 and in cantilever form. This movable plate 1106 is fixed at its one end to a plate base (support member) 1107 formed by patterning photosensitive resin on a wall of the liquid flow channel 1103 or the element substrate 1101. Thereby, the movable plate 1106 is held on the plate base 1107, with a fulcrum (support portion) 1108.
By making the movable plate 1106 like a comb-tooth, it can be fabricated simply and easily, and the alignment for the plate base 1107 can be made easily.
This movable plate 1106 is disposed at a position facing and covering the heat generator 1102, about 15 xcexcm away, so as to have the fulcrum (support portion: fixed end) 1108 upstream in the great flow passing from the common liquid chamber 1105 via above the movable plate 1106 to the discharge opening 1104 by operation of discharging the liquid, and the free end downstream of this fulcrum 1108. A bubble producing region 1110 is between this heat generator 1102 and the movable plate 1106.
By generating heat with the heat generator 1102 and applying that heat to the liquid in the bubble producing region 1110 between the movable plate 1106 and the heat generator 1102, a bubble 1111 is produced in that liquid, based on the film boiling phenomenon as described in U.S. Pat. No. 4,723,129 (see FIG. 19B). The pressure caused by the produced bubble 1111 will act predominantly on the movable plate 1106, to displace the movable plate 1106 around the fulcrum 1108 to be open toward the discharge opening 1104, as shown in FIGS. 19B, 19C or FIGS. 20A and 20B. By displacement of the movable plate 1106 or displaced state, the pressure caused by produced bubble 1111 is propagated or the growth of bubble 1111 itself led to the discharge opening 1104. At this time, the top end portion of the free end 1109 has a width, which makes it easier to lead bubbling power of the bubble 1111 to the discharge opening 1104, with radical improvements in the discharge efficiency of liquid droplet, discharge power or discharge rate.
As described above, a technique disclosed in Japanese Patent Application Laid-Open No. 9-201966 is one in which the positional relation between the fulcrum of movable plate and the free end in the liquid channel is locating the free end on the discharge opening side or downstream, and the production of a bubble is positively controlled by disposing the movable plate opposed to the heat generator or bubble producing region.
Another example of a conventional liquid discharge head is shown in FIG. 20B. Each constitution of an element substrate 1201, a heat generator 1202, a liquid flow channel 1203, a discharge opening 1204, a common liquid chamber 1205 and a bubble producing region 1209 for the liquid discharge head as shown in FIG. 20B is the same as that of the liquid discharge head as shown in FIG. 20A, and ] a material that contains silicon as the material thereof. More specifically, it is preferable to use silicon nitride, silicon oxide, or silicon carbide.
Also, it is preferable to have an oxide thin film between each layer constituting said movable plate to suppress the grain growth of each layer of material containing silicone more effectively. As above described, the movable plate made of material containing silicon can be formed by plasma CVD.
Further, the outer peripheral end face of the movable member may be in the form of saw teeth in the thickness direction of the movable member.
In this respect, although described in the embodiments in detail below, one-time film formation process of the present invention is the film formation process where the density, composition, and the like of the film formed in each process are different on the substrate side thereof and on the side opposite thereto. For example, if the temperature changes are repeated several cycles in continuation in the CVD apparatus, it is assumed that one cycle portion thereof is the one-time film formation process.
In order to achieve the above objects, according to the present invention, there is provided a liquid discharge head, according to other embodiment, at least comprising a discharge opening for discharging the liquid, a liquid flow channel in communication with said discharge opening and for supplying said liquid to said discharge opening, a substrate equipped with a heat generator for producing a bubble in the liquid that is filled in the liquid flow channel, and a movable plate supported and fixed onto said substrate at a position of said substrate opposed to said heat generator and with a gap from said substrate, with a free end on the discharge opening side, said liquid discharge head discharging the liquid from the discharge openings by forcing the free end of said movable plate to be displaced toward said discharge opening around a fulcrum portion made near a support and fixing portion of said movable plate with said substrate due to pressure caused by produced bubble. The movable member is formed in a structure where three layers or more are laminated, each with a layer having different Young""s modulus from the adjacent area.
Here, the xe2x80x9clayerxe2x80x9d of the present invention is different from the xe2x80x9cfilmxe2x80x9d formed in the aforesaid one-time film formation process, but it indicates one whose density and composition are different from the adjacent layer. In this respect, the layer may present a definite separation from the adjacent one. However, a layer that does not show any definite separation from the adjacent layer is assumed to be included in the term xe2x80x9clayerxe2x80x9d of the present invention.
In accordance with the structure described above, the three layers or more are formed in a laminated structure each having different Young""s modulus from the adjacent area. Therefore, the growth of grains within the movable plate can be suppressed to cut off linkage of the grain boundary, providing a greater allowance of flexibility for the movable portion (particularly the fulcrum portion) accompanied with displacement of the movable plate, resulting in increased strength of the movable plate and more durability of the movable plate.
Furthermore, it is preferred that said movable plate has such a structure that a layer made of a material having a relatively low Young""s modulus is sandwiched between the layers of a material having a relatively high Young""s modulus.
In addition, the material having a relatively low Young""s modulus may be silicone oxide, and the material having a relatively high Young""s modulus may be silicon nitride or silicon carbide. Also, the alloy containing aluminum may be Alxe2x80x94Cu, Alxe2x80x94Ni, Alxe2x80x94Cr, Alxe2x80x94Co, or Alxe2x80x94Fe. The plate base between the support and fixing portion of said movable plate and the substrate can provide the increased strength of connecting the support and fixing portion of the movable plate with the substrate is increased and the greater mechanical durability of the movable plate.
Further, the material for the plate base may contain Ti, or tantalum.
Also, in accordance with still another embodiment of the present invention, the liquid discharge head is provided with at least the discharge ports for discharging liquid, the liquid flow paths communicated with the discharge ports for supplying the liquid to the discharge ports, the substrate provided with heat generating elements for creating bubbles in the liquid filled in each of the liquid flow paths; and the movable members arranged in the position facing the heat generating elements on the substrate with a gap to it, and supported and fixed on the substrate with the free end thereof being on the discharge port side, and this liquid discharge head discharges the liquid from the discharge ports by displacing the free end of the movable members to the discharge port side centering on the fulcrum structured near the supporting and fixing portion of the movable members with the substrate. For this head, the outer peripheral end face of the movable member is in the form of saw teeth in the thickness direction of the movable member.
Here, the phrase xe2x80x9cin the form of saw teeth in the thickness directionxe2x80x9d in the description of the present invention means the area and outer circumferential length of the section orthogonal to the thickness direction of the movable member which are caused to change larger to smaller to larger in that order, respectively, for example.
When ink flows in the nozzle by the development and extinction of the bubble created by the heat generating element to displace the movable member, turbulent occurs due to the outer peripheral end face of the saw teeth shape of the kind. As a result, even if ultrafine bubbles are allowed to reside in each of the flow paths and the common liquid chamber, a turbulence acts to promote the discharge of such fine bubbles through each of the discharge ports, thus suppressing them to move toward the common liquid chamber side.
Also, in accordance with still another embodiment of the present invention, the liquid discharge head is provided with at least the discharge ports for discharging liquid, the liquid flow paths communicated with the discharge ports for supplying the liquid to the discharge ports, and the substrate provided with the heat generating elements for creating bubbles in the liquid filled in each of the liquid flow paths; and the movable members arranged in the position facing the heat generating elements on the substrate with a gap to it, and supported and fixed on the substrate with the free end thereof being on the discharge port side, and this liquid discharge head discharges the liquid from the discharge ports by displacing the free end of the movable members to the discharge port side centering on the fulcrum structured near the supporting and fixing portion of the movable members with the substrate. For this head, the outer peripheral and face of the movable member is in the form of saw teeth in the direction intersecting the thickness direction of the movable members.
Here, the phrase xe2x80x9cin the form of saw teeth in the direction intersecting the thickness directionxe2x80x9d in the description of the present invention means an arbitrary outer circumferential section orthogonal to the thickness direction of the movable member, which is provided with fine irregular portions.
For the structure described above, ink layer is present between fine gaps between the nozzle side walls and movable members, respectively. With the ink flow in each nozzle which takes place by the development and extinction of the bubble created by each heat generating element, each movable member is displaced vertically. At this juncture, slide stress acts upon the movable member. In order to enhance the response capability of the movable member, there is a need for reducing this slide stress. However, since the ink layer is present in the fine gap between the nozzle side walls and each movable member, it becomes possible to reduce the slid stress without spoiling the function of each movable member to suppress the ink flow to the backward side, hence improving the response capability of each movable member.
Also, in accordance with still another embodiment of the present invention, the liquid discharge head is provided with at least the discharge ports for discharging liquid, the liquid flow paths communicated with the discharge ports for supplying the liquid to the discharge ports, and the substrate provided with the heat generating elements for creating bubbles in the liquid which is filled in each of the liquid flow paths, and the movable members arranged in the position facing the heat generating elements on the substrate with a gap to it, and supported and fixed on the substrate with the free end thereof being on the discharge port side, and this liquid discharge head discharges the liquid from the discharge ports by displacing each free end of the movable members to the discharge port side centering on the fulcrum structured near the supporting and fixing portion of the movable members with the substrate. For this liquid discharge head, the density of the material that forms the movable members on the bonding area with the substrate is smaller than the density of the material that forms the movable members in other areas.
Also, in accordance with still another embodiment of the present invention, the liquid discharge head is provided with at least the discharge ports for discharging liquid, the liquid flow paths communicated with the discharge ports for supplying the liquid to the discharge ports, and the substrate provided with the heat generating elements for creating bubbles in the liquid which is filled in each of the liquid flow paths, and the movable members arranged in the position facing the heat generating elements on the substrate with a gap to it, and supported and fixed on the substrate with the free end thereof being on the discharge port side, and this liquid discharge head discharges the liquid from the discharge ports by displacing each free end of the movable members to the discharge port side centering on the fulcrum structured near the supporting and fixing portion of the movable members with the substrate. For this liquid discharge head, the pedestal portion is arranged between the supporting and fixing portion of the movable members and the substrate, and at the same time, the density of the material for the formation of the movable members in the bonding area with the pedestal portion is smaller than the density of the material for the formation of the movable members in the other area.
With the structure as described above, the sparse region is formed on the bonding area with the substrate surface of the movable members (or the pedestal portion), hence making it possible to suppressing the abrupt changes of stress when the movable members are formed. As a result, the bonding force becomes stronger between the movable members and the substrate surface (or the pedestal portion) on the bonding area. Then, when the free ends of the movable members are displaced by the pressure exerted by the creation of bubbles for the utilization of discharging liquid, the discharge characteristics are stabilized for the provision of a highly reliable liquid discharge head.
A cartridge of the invention has the liquid discharge head of the invention and a liquid container for holding the liquid to be supplied to the liquid discharge head.
A liquid discharge apparatus of the invention has the liquid discharge head of the invention and drive signal supplying means for supplying a drive signal to discharge the liquid from the liquid discharge head.
Also, a manufacturing method of the liquid discharge head of the invention comprising a discharge opening for discharging the liquid, a liquid flow channel in communication with said discharge opening and for supplying said liquid to said discharge opening, a substrate equipped with a heat generator for producing a bubble in the liquid that is filled in the liquid flow channel, and a movable plate supported and fixed onto said substrate at a position of said substrate opposed to said heat generator and with a gap from said substrate, with a free end on the discharge opening side, said liquid discharge head discharging the liquid from the discharge openings by forcing the free end of said movable plate to be displaced toward said discharge opening around a fulcrum portion made near a support and fixing portion of said movable plate with said substrate due to pressure caused by produced bubble is characterized by including a process of building up a gap formation member for forming said gap on said substrate, a first step of forming film for use of the movable members for the film formation of the substrate portion becoming the movable members on the substrate and the gap formation members, a second step of forming film for use of the movable members for the further film formation of the substrate portion becoming the movable members after the first step of forming the substrate film for use of the movable members, a process of forming said movable plate by patterning a base portion for said movable plate, and a process for removing said gap formation member.
By the manufacturing method as above, a movable plate superior in durability can be fabricated by providing several processes for forming the base portion for the movable plate. The material of the base portion for the movable plate desirably contains silicon, and specifically, may be silicon nitride, silicon oxide or silicon carbide.
Also, in layering the material containing silicon, an oxide film is formed on the surface of the material containing silicon, and a next layer is formed on this oxide thin film, suppressing the grain growth between each layer owing to the oxide thin film, resulting in greater durability of the movable plate. Such oxide thin film can be formed by leaving away the substrate in the atmosphere after forming the layer of the material containing silicon in vacuum, and particularly, the layer of the material containing silicon can be formed by plasma CVD.
Furthermore, the gap formation member may be formed by sputtering aluminum or aluminum alloy, and removed by wet etching with a mixture liquid of acetic acid, nitric acid, and hydrochloric acid. Thereby, the peripheral end face of the movable plate can be made the saw-tooth configuration.
Another manufacturing method of the liquid discharge head of the invention comprising a discharge opening for discharging the liquid, a liquid flow channel in communication with said discharge opening and for supplying said liquid to said discharge opening, a substrate equipped with a heat generator for producing a bubble in the liquid that is filled in the liquid flow channel, and a movable plate supported and fixed onto said substrate at a position of said substrate opposed to said heat generator and with a gap from said substrate, with a free end on the discharge opening side, said liquid discharge head discharging the liquid from the discharge openings by forcing the free end of said movable plate to be displaced toward said discharge opening around a fulcrum portion made near a support and fixing portion of said movable plate with said substrate due to pressure caused by produced bubble, includes a process of forming a pad protective layer for protecting a pad for electrical connection on said substrate, a process of forming a gap formation member for forming said gap on said substrate and said pad protective layer, a process of laminating layers each having different Young""s modulus from the adjacent area in three or more layers forming a movable plate base portion which serves as the movable plate on said substrate, said pad protective layer and said gap formation member, a process of forming said movable plate by patterning said movable plate base portion, a process for removing said gap formation member, and a process of removing an exposed portion of said pad protective layer.
Thereby, the liquid discharge head can be fabricated with increased allowance for flexibility of the movable portion (particularly fulcrum portion) accompanied with the displacement of the movable plate, which provides the greater strength of the movable plate and enhanced durability of the movable plate.
Further, the process of forming the movable plate by patterning the movable plate base portion preferably includes a subprocess of forming a structure in which the layer having relatively low Young""s modulus is sandwiched between the layers having relatively high Young""s modulus.
Also, in accordance with still another embodiment of the present invention, a method for manufacturing a liquid discharge head, which is provided with discharge ports for discharging liquid; liquid flow paths communicated with the discharge ports for supplying the liquid to the discharge ports; the substrate provided with the heat generating elements for creating bubbles in the liquid filled in each of the liquid flow paths; and movable members arranged in the position facing the heat generating elements on the substrate with a gap thereto, and supported and fixed on the substrate with the free end thereof being on the discharge port side, and the liquid being discharged from the discharge ports by displacing the free end of the movable members to the discharge port side centering on the fulcrum structured near the supporting and fixing portion of the movable members with the substrate, comprises the steps of: forming the pad protection layer on the substrate to protect pads for use of electrical connection; forming the gap formation members on the substrate and the pad protection layer for the formation of the gap; forming the substrate portion for use of the movable members becoming the movable members on the pedestal portion, the pad protection layer, and the gap formation members so as to make the density of material for the formation of the movable members smaller in the bonding area with the pedestal portion than the density of material for the formation of the movable members in the other area; forming the movable members by patterning the substrate portion for use of the movable members; removing the gap formation members; and removing the exposed portion of the pad protection layer.
Further, in accordance with still another embodiment of the present invention, a method for manufacturing a liquid discharge head, which is provided with discharge ports for discharging liquid; liquid flow paths communicated with the discharge ports for supplying the liquid to the discharge ports; the substrate provided with the heat generating elements for creating bubbles in the liquid filled in each of the liquid flow paths; and movable members arranged in the position facing the heat generating elements on the substrate with a gap thereto, and supported and fixed on the substrate with the free end thereof being on the discharge port side, and the liquid being discharged from the discharge ports by displacing the free end of the movable members to the discharge port side centering on the fulcrum structured near the supporting and fixing portion of the movable members with the substrate, comprises the steps of forming the pad protection layer on the substrate to protect pads for use of electrical connection; forming the pedestal portion to be arranged between the supporting and fixing portion of the movable members and the substrate; forming the gap formation members on the substrate and the pad protection layer for the formation of the gap; forming the substrate portion for use of the movable members becoming the movable members on the pedestal portion, the pad protection layer, and the gap formation members go as to make the density of material for the formation of the movable members smaller in the bonding area with the substrate than the density of material for the formation of the movable members in the other area; forming the movable members by patterning the substrate portion for use of the movable members; removing the gap formation members; and removing the exposed portion of the pad protection layer.